The Massaqueraman (spelling?)

I have a problem with this one, we didn't find out much about him. He was supposed to be half fish, half man with teeth like those of a peerai (piranha.) But he lived in rivers and creeks of the rain-forests, so we were'nt worried about him. After all, he was far away and would hardly swim up the Demerara river to get us.
Unlike his female counterpart the fair-maid who was beguilinly beatutifuh, he was mosterously ugly.

Hmm.... wonder if this fishy monster is related to masquerade-man?